DUAL TRANSDUCTION SIGNALING BY A XENOPUS MUSCARINIC RECEPTOR - ADENYLYL-CYCLASE INHIBITION AND MAP KINASE ACTIVATION

Using transient transfection of COS-7 and human embryonic kidney 293 c ells, we studied the functional properties of a previously cloned musc arinic Xenopus receptor [Herrera et al. (1994): FEBS Lett 352:175-179] and its coupling to adenylyl cyclase (AC) and mitogen-activated prote in kinase (MAPK) pathways. Expression of the Xenopus muscarinic recept or results in the inhibition of AC activity and activation of the MAPK pathway through a mechanism that involves a Pertussis-toxin-sensitive G-protein and the G beta gamma subunits. The signal transduction prop erties of this receptor are similar to the mammalian m2 and m4 muscari nic receptors. These results strongly support the idea that inhibition of AC and MAPK activation, signaled out from the muscarinic oocyte re ceptor, are involved in the oocyte maturation process. (C) 1997 Wiley- Liss, Inc.